Future

Returns whether the future has already been completed with a value or an exception.

Note: using this method yields nondeterministic dataflow programs.

When this future is completed, either through an exception, or a value, apply the provided function.

If the future has already been completed, this will either be applied immediately or be scheduled asynchronously.

Multiple callbacks may be registered; there is no guarantee that they will be executed in a particular order.

The provided callback always runs in the provided implicit ExecutionContext, though there is no guarantee that the execute() method on the ExecutionContext will be called once per callback or that execute() will be called in the current thread. That is, the implementation may run multiple callbacks in a batch within a single execute() and it may run execute() either immediately or asynchronously.

Await the "completed" state of this Awaitable.

This method should not be called directly; use Await.ready instead.

Await and return the result (of type T) of this Awaitable.

This method should not be called directly; use Await.result instead.

The value of this Future.

If the future is not completed the returned value will be None. If the future is completed the value will be Some(Success(t)) if it contains a valid result, or Some(Failure(error)) if it contains an exception.

Applies the side-effecting function to the result of this future, and returns a new future with the result of this future.

This method allows one to enforce that the callbacks are executed in a specified order.

Note that if one of the chained andThen callbacks throws an exception, that exception is not propagated to the subsequent andThen callbacks. Instead, the subsequent andThen callbacks are given the original value of this future.

The following example prints out 5:

val f = Future { 5 }
f andThen {
  case r => sys.error("runtime exception")
} andThen {
  case Failure(t) => println(t)
  case Success(v) => println(v)
}

Creates a new future by mapping the value of the current future, if the given partial function is defined at that value.

If the current future contains a value for which the partial function is defined, the new future will also hold that value. Otherwise, the resulting future will fail with a NoSuchElementException.

If the current future fails, then the resulting future also fails.

Example:

val f = Future { -5 }
val g = f collect {
  case x if x < 0 => -x
}
val h = f collect {
  case x if x > 0 => x * 2
}
Await.result(g, Duration.Zero) // evaluates to 5
Await.result(h, Duration.Zero) // throw a NoSuchElementException

Returns a failed projection of this future.

The failed projection is a future holding a value of type Throwable.

It is completed with a value which is the throwable of the original future in case the original future is failed.

It is failed with a NoSuchElementException if the original future is completed successfully.

Blocking on this future returns a value if the original future is completed with an exception and throws a corresponding exception if the original future fails.

Creates a new future which holds the result of this future if it was completed successfully, or, if not, the result of the that future if that is completed successfully. If both futures are failed, the resulting future holds the throwable object of the first future.

Using this method will not cause concurrent programs to become nondeterministic.

Example:

val f = Future { sys.error("failed") }
val g = Future { 5 }
val h = f fallbackTo g
Await.result(h, Duration.Zero) // evaluates to 5

Creates a new future by filtering the value of the current future with a predicate.

If the current future contains a value which satisfies the predicate, the new future will also hold that value. Otherwise, the resulting future will fail with a NoSuchElementException.

If the current future fails, then the resulting future also fails.

Example:

val f = Future { 5 }
val g = f filter { _ % 2 == 1 }
val h = f filter { _ % 2 == 0 }
Await.result(g, Duration.Zero) // evaluates to 5
Await.result(h, Duration.Zero) // throw a NoSuchElementException

Creates a new future by applying a function to the successful result of this future, and returns the result of the function as the new future. If this future is completed with an exception then the new future will also contain this exception.

Example:

val f = Future { 5 }
val g = Future { 3 }
val h = for {
  x: Int <- f // returns Future(5)
  y: Int <- g // returns Future(3)
} yield x + y

is translated to:

f flatMap { (x: Int) => g map { (y: Int) => x + y } }

Asynchronously processes the value in the future once the value becomes available.

Will not be called if the future fails.

Creates a new future by applying a function to the successful result of this future. If this future is completed with an exception then the new future will also contain this exception.

Example:

val f = Future { 5 }
val g = Future { 3 }
val h = for {
  x: Int <- f // returns Future(5)
  y: Int <- g // returns Future(3)
} yield x + y

is translated to:

f flatMap { (x: Int) => g map { (y: Int) => x + y } }

When this future is completed with a failure (i.e., with a throwable), apply the provided callback to the throwable.

The future may contain a throwable object and this means that the future failed. Futures obtained through combinators have the same exception as the future they were obtained from. The following throwable objects are not contained in the future:

• Error - errors are not contained within futures
• InterruptedException - not contained within futures
• all scala.util.control.ControlThrowable except NonLocalReturnControl - not contained within futures

Instead, the future is completed with a ExecutionException with one of the exceptions above as the cause. If a future is failed with a scala.runtime.NonLocalReturnControl, it is completed with a value from that throwable instead.

If the future has already been completed with a failure, this will either be applied immediately or be scheduled asynchronously.

Will not be called in case that the future is completed with a value.

Multiple callbacks may be registered; there is no guarantee that they will be executed in a particular order.

The provided callback always runs in the provided implicit ExecutionContext, though there is no guarantee that the execute() method on the ExecutionContext will be called once per callback or that execute() will be called in the current thread. That is, the implementation may run multiple callbacks in a batch within a single execute() and it may run execute() either immediately or asynchronously.

When this future is completed successfully (i.e., with a value), apply the provided partial function to the value if the partial function is defined at that value.

If the future has already been completed with a value, this will either be applied immediately or be scheduled asynchronously.

Multiple callbacks may be registered; there is no guarantee that they will be executed in a particular order.

The provided callback always runs in the provided implicit ExecutionContext, though there is no guarantee that the execute() method on the ExecutionContext will be called once per callback or that execute() will be called in the current thread. That is, the implementation may run multiple callbacks in a batch within a single execute() and it may run execute() either immediately or asynchronously.

Creates a new future that will handle any matching throwable that this future might contain. If there is no match, or if this future contains a valid result then the new future will contain the same.

Example:

Future (6 / 0) recover { case e: ArithmeticException => 0 } // result: 0
Future (6 / 0) recover { case e: NotFoundException   => 0 } // result: exception
Future (6 / 2) recover { case e: ArithmeticException => 0 } // result: 3

Creates a new future that will handle any matching throwable that this future might contain by assigning it a value of another future.

If there is no match, or if this future contains a valid result then the new future will contain the same result.

Example:

val f = Future { Int.MaxValue }
Future (6 / 0) recoverWith { case e: ArithmeticException => f } // result: Int.MaxValue

Creates a new future by applying the 's' function to the successful result of this future, or the 'f' function to the failed result. If there is any non-fatal exception thrown when 's' or 'f' is applied, that exception will be propagated to the resulting future.

Zips the values of this and that future, and creates a new future holding the tuple of their results.

If this future fails, the resulting future is failed with the throwable stored in this. Otherwise, if that future fails, the resulting future is failed with the throwable stored in that.